Spark plug



M. H. LUDE Feb, 17,v 1942.

SPARKPLUG Filed Sept. 2e, 1940 lm; AI

fn deff/fr: Maw J7( wie u -Patented Feb. 17, 1942' 2,273,651 SPARK PLUGMax H. Lude, Greenville, lll., assigner to Thoma. & Gould Sales Company,St. Louis, Mo., a rm composed of Walter C. Thoma and Herman C.

Gould Application September 26, 1940, Serial No. 358,398 cclaims. (el.12a- 169) This invention relates to spark plugs.

Objects of the invention are to provide an improved spark plug having ametallic shell adapted to be screwed-into a threaded hole opening intothe combustion space of an internal combustion engine, and having a sideelectrode attached to its inner end and enclosing a central insulatingbody having a center electrode projecting beyond each end thereof, andmeans for securing said insulating body in said shell in either one oftwo positions to place either of said vcenter electrodes in cooperativerelationship to the side electrode; to form said shell with means orpassages through which air may be circulated to cool the spark plug andparticularly said insulating body by currents or blasts of air driventhrough said passages by the usual fan mounted adjacent to the engine;to provide an insulation holder having an adjustable terminal forengaging the electrode on the outer end of said insulating lbody whichis also in electrical communication with the center electrode that is incooperative relationship with the side electrode; to provide means forventing or passing air through said insulation holder outwardly beyondthe shell to cool the same and the parts contained therein; to providenovel center electrodes extending beyond opposite ends of the centralinsulating body and in electrical communication or contact with eachother whereby the spark plug may be made to function properlyirrespective of reversal of its position in the shell; to provide thecentral insulating body with `a novel formationof insulating shouldersaffording more surface to transfer heat therefrom; to provide a terminalattaching screw adjustably mounted in the insulation holder whereby theposition of said attaching screw may be varied or changed as required bythe dimensions of the electrode in the central insulating body; and toprovide suitable sealing gaskets arranged in a novel relationshipbetween the elements of the spark plug to render the same completelyimpervious and leakproof.

Another object of the invention is to provide an improvedcentral"insulating body having duplicate center electrodes extendingfrom its opposite ends and'also having a non-blistering type of glaze onits end portions that are exposed to the combustion forces within theengine so as toprolong and extend the life of the spark plug, and alsoto provide blunt or rounded ends on the central insulating body to avoidspreading by compression, as sometimes occurs in spark plugs havingconcavities in the inner ends of the insulating elements supporting thecenter electrode.

Other objects will appear from the following description, referencebeing made to the annexed drawing, in which- Fig'. 1 is a side elevationof a spark plug embodying the present invention.

Fig. 2 is a longitudinal sectional view of the spark plug.

Fig. 3 is a side elevation of the reversible central insulating bodyhaving a center. electrode extending beyond each end thereof.

The metallic shell I is formed with an externally threaded end 2 whichis adapted to be screwed into a threaded hole opening into thecombustion space of an internal combustion engine. A side electrode 3 isattached to the inner end of the shell. The shell is formed with acircumferential shoulder 4 which is arranged to engage and compress asealing gasket or Washer 5 against the engine body to provide aleak-proof joint. 'Ihe outer end 6 of the shell is polygonal and isadapted to be engaged by a wrench or the like to attach and detach thespark plug. The

shell is formed with a series of passages l through shoulder I3 in theshell and against the inner shoulder l0, thereby forming a leakproofseal.

In this assembly, a sealing gasket or washer Il seats-against the outershoulder lI I. y

Electrodes I5 and I6 are embedded within the central msumting body andproject beyond oppo-` site ends thereof so that, vwhen the spark plug isassembled, one of said electrodes extends slightly beyond the inner endof the shell adjacent to the outer electrode 3 in position to cooperatetherewith vwhen enerized. The two electrodes, l5 and i6 are inelectrical contact with each other by a telescoping joint I1, and eachof saidelectrodes hasan enlarged circumferential flange or head I8 onits outer end. The ends I9 of the central insulating body aresubstantially iiat or blunt, as distinguished from the present practiceof forming the yinner end of the insulation element supporting thesingle center electrode slightly hollow or concave. Forming the endsblunt or hat avoids spreading oi vthe insulation body around the centerelectrode by compression within the combustion chamber of the engine.These insulating elements may be made oi any suitable material, such asporcelain or glass or fiber. vThe ends are formed with a non-glisteningtype of glaze, as distinguished from the enamel type of glaze in orderto cooperate with the shoulders lll and II to transfer or dissipate heatfrom the spark plug when in use A hollow tapered insulating element 2Uextends into the outer end of the shell, encloses the outer end portionof the insulating body bearing the center electrode, and seats againstthe sealing gasket or washer I4. A clamping gland or nut 2l encloses andis attached to the inner end of the element 20 and screws into theinternally threaded outer end of the shell, thereby clamping all of theparts rigidly in assembled cooperative relationship. The element 20 maybe formed with a number of air passages 22 to permit flow of airtherethrough to assist in cooling the spark plug. The nut orl gland 2|is formed with a wrench engaging polygonal portion 2l to facilitateattachment and detachment thereof.

vThe terminal 2l is screwed into a threaded hole in the outer end of theelement 2li in order to effect electrical contact with the outwardlyextended center electrode l5 or IB, depending upon the position of theinsulating body Il within the shell. When either of the centerelectrodes becomes burnt or otherwise shortened, the spark plug may .betaken apart and the insulating body 8 reversed to place the damagedelectrode at the outer end and the undamaged electrode at the inner end.The terminal element 24 may then be screwed further into the member 20to effect electrical contact with the shortened or damaged electrodeadjacent thereto. A flange or shoulder 25 is formed on the terminal 2lin position to permit longitudinal adiustment of said terminal asdescribed, and still support the attached wire. A nut 2B is screwed onthe threaded outer end of the terminal 2l to hold the wire clampedagainst the shoulder 2l.

The electrodes l5 and I6 are preferably cemented within the body 8 andheld in rigid relationship therein by liquid porcelain cement or otherattaching means.l

It should now be apparent that this invention constitutes an improvedspark plug attaining all of its intended objects and purposes in ahighly emcient, economical and satisfactory way. 'I'he 4spark plug maybe made and sold at permissible,

cost and will endure substantially twice as long as spark plugs ofstandard construction having a single non-reversible andnon-'replaceable center electrode. The invention may be varied x withinthe scope of equiv lent limits without de'-r and principle thereof.

tion, an insulating body removably mounted inA said shell, centerelectrodes projecting beyond the ends of said insulating body andadapted to cooperate with said outer electrode, means for supportingsaid insulating body inV alternativepositions in said shell in whicheither selected se of said center electrodes is adjacent 'to saidagainst. said body, and a terminal adjustably4 supported by said elementand adapted to engage the outer one oi said center electrodes.

f2. A spark plug comprising a metallic shell having an outer electrodeattached to its inner end, a pair of oppositely extended centerelectrodes, an insulating body for supporting said center electrodes inalternative positions in which either selected one of said centerelectrodes is adjacent to said outer electrode and the other centerelectrode extends outwardly, an insulating element for clamping saidbody in said shell, a wire attaching terminal mounted in said elementand insulated thereby from said shell and having electrical contact withsaid center electrode that extends outwardly, and means for conductingair through said shell for cooling the spark plug.

3. A spark plug comprising a metallic shell having an outer4 electrodeattached to its inner end, a removable and replaceable insulating bodysupported in said shell, a pair of center electrodes extendingl .beyondthe opposite ends of said insulating body, means for supporting saidinsulating body in alternative positions in said shell in which eitherselected one of said center electrodesis adjacent to said outerelectrode. an insulating element engaging said body, a terminalattaching member adjustably suported by said element and insulatedthereby'from said shell and having electrical contact with the outer oneof said center electrodes, and a clamping gland engaged with said shellandsaid insulating element and holding said element and said body inrigid engagement with each other.

4. A spark plug comprising a metallic shell having an outer electrodeattached to its inner end, a removable and replaceable insulating bodysupported in said shell, a pair of center electrodes extending beyondthe opposite ends of said insulating body, means for supporting saidinsulating body in alternative positions in said shell in which eitherselected one of said center electrodes is adjacent to said outerelectrode, an insulating element engaging said body, a terminalattaching member adjustably supported by said element and insulatedthereby fromv said shell and having electrical contact with the outerone of said center electrodes, a clamping gland engaged with said shelland said insulating element and holding said element and said body inrigid engagement with each other, -and means for conducting air throughsaid shell about said insulating body.

5. A spark plug comprising a metallic shell having an outer electrodeattached to its inner end, a removable and replaceable insulating bodysupported in said shell, a pair of center electrodes extending beyondthe opposite ends of said insulating body, means for supporting saidinsulating body in alternative positions in said shell in which eitherselected one of said center electrodes is adjacent to said outerelectrode, an insulating elementengaglng said body, a terminal attachingmember adjustably supported by said element and insulated thereby fromsaid shell and having electrical contact with the, outer one of saidcenter electrodes, a clamping gland engaged with said shell and saidinsulating element and holding said body and said element in rigidengagement with each other, and means for conducting air about the outerone of said inner electrodes.

6, A spark plug comprising a metallic shell having an outer electrodeattached to its inner end, a removable and replaceable insulating bodysupported in said shell, a, pair of center electrodes extending beyondthe ODPQSite .ends

'of' said insulating bodyand having'V electrical contact with each otherwithin said body, means for supporting said insulating body inalternative positions in said shell to hold either selected one of saidcenter electrodes adjacent to said outer electrode and to hold` the`other center "through out of communication with the interior v of saidshell, a terminal attaching member ad justably supported by said elementand having velectrical contact with the outer one of said centerelectrodes, and a clamping gland screwed in the outer end of said shelland holding said insulating .element and .said body in rigidrelationship with each other and also in rigid relationship with said.shell,

